Beneficiaries Equity of the Parent Company - Number of Shares and Net Income Used to Calculate Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator
Net income (loss)	$ (43,262)	$ 19,046	$ 14,579	$ 48,015
Net (income) loss attributable to noncontrolling interests, Basic	339	(170)	(167)	(384)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(80)	(73)	(280)	(245)
Distribution to preferred shareholders	0	0	0	(2,032)
Preferred share redemption charge	0	0	0	(3,181)
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust	(43,003)	18,803	14,132	42,173
Net (income) loss attributable to noncontrolling interests, Diluted	339	(170)	(167)	(384)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	(80)	(73)	(280)	(245)
Net income (loss) attributable to common shareholders, Diluted	$ (43,003)	$ 18,803	$ 14,132	$ 42,173
Denominator
Basic weighted average shares outstanding (in shares)	178,602,622	175,433,657	178,515,993	175,315,581
Contingent securities/Share based compensation (in shares)	0	1,401,365	1,236,551	1,283,751
Diluted weighted average shares outstanding (in shares)	178,602,622	176,835,022	179,752,544	176,599,332
Earnings (loss) per Common Share:
Net income (loss) attributable to common shareholders, Basic (USD per share)	$ (0.24)	$ 0.11	$ 0.08	$ 0.24
Net income (loss) attributable to common shareholders, Diluted (USD per share)	$ (0.24)	$ 0.11	$ 0.08	$ 0.24